This invention relates generally to the field of exercise equipment, and more specifically, exercise equipment having an electrical generating means. Systems and methods to produce electrical power derived from a human exercise motion, herein referred to as human-input, are known and have been reduced to practice in commercial exercise equipment products. Commercial has generally been limited to exercise products intended for cardiovascular exercise such as stationary bicycles. prior devices used for converting kinetic energy caused by human input generally includes at least one electrical generator and associated control and/or display electronics; these devices are generally referred to as an energy harvester in this disclosure. The electrical power produced is often used to provide power to an electronics load, generally known as fitness feedback electronics, typically comprising LCD displays, sensors, and communication electronics. In some examples, the equipment derives electrical power entirely from the human input, without a need to plug into an external electrical outlet. In exercise equipment that is of the strength training type, methods to produce electrical power by converting human input have been disclosed in prior literature, however the methods have generally had substantial limitations in performance.
For instance, prior systems and methods employ energy harvesters that couple directly and rigidly to a translating or rotating member of the equipment in a manner that may cause undesired ripple forces and torques. That is, that arise during a process of electromechanical energy conversion are transmitted to the user, either through the seat or the user's grip, resulting in an objectionable exercise feel to the user. The undesired forces also can result in the generation of objectionable acoustic noise, for example inducing vibrations in the lightly damped, mechanically stiff frame of exercise equipment that resonate at frequencies in the audible range. One example of a source of undesired ripple force is cogging torque in an electrical generator.
Prior art methods have disclosed energy harvesters that have rigid or semi-rigid mechanical coupling directly to an existing pulley or moving member of the exercise equipment, other than the weight stack. These prior-art arrangements generally require significant modification to the standard exercise equipment design in order to realize proper mechanical attachment of the generator, sensors, or other electronic devices. The modifications required for one equipment type, (e.g., a biceps machine), may generally not be compatible with the other types.
Another drawback of prior art methods, especially methods that rely on engagement or attachment to existing equipment pulleys, is that they are not well-suited to strength equipment that incorporates independent motion arrangements (e.g., left and right bodily motion arrangements) with a common weight stack. This type of strength equipment has become popular in the market due to its ability to emulate a “free weight” user experience. For this type of equipment, methods disclosed in the prior art generally require the use of two energy harvesters to guarantee functional operation when a user chooses to utilize only a portion (e.g., left or right side) of the motion arrangement.
Generally, the prior art methods are mechanically coupled to a rotating pulley that also provides a function to guide the main cable (or belt) of the strength equipment. In this arrangement, the energy harvester must apply torque to the pulley. To function properly, the torque applied to the pulley by the energy harvester must be limited to avoid slip between the pulley and the main cable, i.e., the torque applied by the energy harvester must be less than the torque capacity due to friction between the main cable and the pulley. When a user selects a relatively low weight, for example 10 pounds, the friction force capacity between the main belt and pulley is generally insufficient to support the function of the energy harvester to produce power from the exercise motion.
Further, as safety is usually a critical issue, prior systems and methods fail to address adequately a failure in the generator or electronics of an energy harvester. Such conditions may result in substantial torque applied to the generator shaft of the energy harvester, the torque is subsequently converted to a proportional force applied to the weight stack of the exercise equipment. Generally, the resulting force associated with a failure condition can be large and sudden and therefore harmful to a user that has a grip and is engaged in an exercise motion. For applications where the user has an exercise objective of rehabilitation or therapy, the occurrence of a large weight stack force is especially unacceptable.